Post-truth was Oxford Dictionaries’ 2016 word of the year, but the word became even more relevant in 2017 as Americans suffered through the first year of a presidency frighteningly indifferent, if not openly hostile, to facts. When it comes to exaggerations, half-truths, and outright fabrications, the Trump presidency is without precedent. According to the Washington Post, Trump “has made 1,628 false or misleading claims over 298 days.” In a more conservative tally that omitted “any statement that could be plausibly defended” and “modest quantitative errors,” the New York Times found that Trump “has told 103 separate untruths, many of them repeatedly,” in his first 10 months in office. Obama told 18 over the entirety of his two terms: “That’s an average of about two a year for Obama and about 124 a year for Trump.”

Beyond the sheer quantity, Trump’s incessant lying is also qualitatively different than his predecessors. Previous presidents would correct their statements when met with contrary evidence, the New York Times points out. But “Trump is different. When he is caught lying, he will often try to discredit people telling the truth.” According to psychologist Bella DePaulo, Trump tells more self-serving lies and more cruel lies (i.e., “told to hurt or disparage others”) than participants in her two decades of research on lying.

But Trump’s lies are not only self-serving. The lies serve to prop up the problematic worldview he peddles to his base.